The invention lies in the field of wireless communications networks and is more particularly concerned with broadcasting data in an ad hoc network.
The invention applies especially but not exclusively to vehicular ad hoc networks (VANETs) in which each communications node is a vehicle able to move along traffic lanes of a predefined road network.
In a vehicular ad hoc network, the mobile nodes form various groups dynamically over time and at any given time the mobile nodes within a group are interconnected but the groups are not connected to one another.
The formation of these groups is linked to traffic conditions, notably to the presence of traffic lights in an urban environment.
Moreover, each group of nodes is formed and disintegrates dynamically as a function of the movement of each mobile node liable to quit the group randomly at any time and to enter another at a later time.
As a result of this, the network suffers frequent changes of topology with a degree of connectivity that varies a great deal over time. Because of this, it is difficult to design algorithms offering high performance that are simple to use to broadcast data via all the nodes of such a network.
In a document entitled “An Information Propagation Scheme for VANETs” published in Proceedings of the 8th International IEEE Conference on Intelligent Transportation Systems, Vienna, Austria, Sep. 13-16, 2005, Thomas D. C. Little and Ashish Agarwal describe a method of broadcasting data in a vehicular ad hoc network in which the data packets propagate in the same direction of movement along a two-way traffic lane using the Directional Propagation Protocol (DPP).
However, the Directional Propagation Protocol requires a mechanism for forming and maintaining groups of nodes that is difficult to use and that may become extremely costly in terms of bandwidth use. Furthermore, that protocol does not provide for optimum broadcasting of data to all mobile nodes moving along a two-way traffic lane.